Drawable学习之-----ScaleDrawable

对另一个drawable资源，基于当前的level，进行尺寸变换的drawable。

文件位置：

res/drawable/filename.xml
文件名即资源名

编译数据类型：

指向 ScaleDrawable的指针。

资源引用：

In Java: R.drawable.filename
In XML: @[package:]drawable/filename

语法：

<?xml version="1.0" encoding="utf-8"?>
<scale
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:drawable="@drawable/drawable_resource"
    android:scaleGravity=["top" | "bottom" | "left" | "right" | "center_vertical" |
                          "fill_vertical" | "center_horizontal" | "fill_horizontal" |
                          "center" | "fill" | "clip_vertical" | "clip_horizontal"]
    android:scaleHeight="percentage"
    android:scaleWidth="percentage" />

元素：

<scale>

定义一个ScaleDrawable，必须作为根元素。

属性：

xmlns:android

String类型。 必须的。定义XML文件的命名空间。必须是 "http://schemas.android.com/apk/res/android".

android:drawable

Drawable 资源。必须的。引用一个drawable资源。

android:scaleGravity

关键字。指定缩放后的gravity的位置。

必须是下面的一个或多个值（多个值之间用”|“分隔），下面的值和描述和上一篇的ClipDrawable一样。

值	描述
top	Put the object at the top of its container, not changing its size.
bottom	Put the object at the bottom of its container, not changing its size.
left	Put the object at the left edge of its container, not changing its size. This is thedefault.
right	Put the object at the right edge of its container, not changing its size.
center_vertical	Place object in the vertical center of its container, not changing its size.
fill_vertical	Grow the vertical size of the object if needed so it completely fills its container.
center_horizontal	Place object in the horizontal center of its container, not changing its size.
fill_horizontal	Grow the horizontal size of the object if needed so it completely fills its container.
center	Place the object in the center of its container in both the vertical and horizontal axis, notchanging its size.
fill	Grow the horizontal and vertical size of the object if needed so it completely fills itscontainer.
clip_vertical	Additional option that can be set to have the top and/or bottom edges of the child clipped toits container's bounds. The clip is based on the vertical gravity: a top gravity clips thebottom edge, a bottom gravity clips the top edge, and neither clips both edges.
clip_horizontal	Additional option that can be set to have the left and/or right edges of the child clipped toits container's bounds. The clip is based on the horizontal gravity: a left gravity clipsthe right edge, a right gravity clips the left edge, and neither clips both edges.

android:scaleHeight

Percentage（百分比）缩放的高度，以百分比的方式表示drawable的缩放。形式例如：100%，12.5%。

android:scaleWidth

Percentage（百分比）缩放的宽度，以百分比的方式表示drawable的缩放。形式例如：100%，12.5%。

示例：

<?xml version="1.0" encoding="utf-8"?>
<scale xmlns:android="http://schemas.android.com/apk/res/android"
    android:drawable="@drawable/logo"
    android:scaleGravity="center_vertical|center_horizontal"
    android:scaleHeight="80%" //表示从高度80% 开始缩放，80%为图片高度最小值。level 0不可见。
    android:scaleWidth="80%"/> //表示从宽度80% 开始缩放，80%为图片宽度最小值。level 0不可见。

参考：

• ScaleDrawable

示例：

在scale.xml中：

<?xml version="1.0" encoding="utf-8"?>
<scale xmlns:android="http://schemas.android.com/apk/res/android"
    android:scaleWidth="50%"
    android:scaleHeight="50%"
    android:drawable="@drawable/image1"
    android:scaleGravity="center_vertical|center_horizontal"
    >
</scale>

在layout中使用：

<ImageView
    android:id="@+id/imgView"
    android:src="@drawable/scale"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>